Lasers have various applications. The determination of any particular application is dependent on both the power and the beam characteristics. Pulse length, energy per pulse, polarization, and coherence length all play a part in the final outcome of the chosen application. Although there are many different types of lasers, as well as many different applications, of particular usefulness for many applications are diode lasers.
Diode lasers have high electrical efficiency and can be set up in an array pattern which can then be scaled to produce a high power. In the past, when such an arrangement was attempted, each emitter (usually 1 of 50 per cm bar, put into a stack) has produced a beam with a separate, differing wavelength (i.e.: color), coherence length, and divergence per emitter.
Laser diode power modules are known to change their peak output frequency with temperature variants, which naturally occur in arrays of laser diodes, typically at a rate of 0.3 nanometers per degree C. This often causes the entire array to operate at different frequencies from the point of turn-on until they have reached overload, with potentially negative results.
Across each emitter bar there is typically a temperature difference from edge to center to opposite edge as electrical power is directed to the device and water is utilized in the prior art in an attempt to remove the temperature differentials. This results in a corresponding color output difference in commercially available diode laser stacks or modules. The effect means that as one attempts to focus this light to a point, each emitter will focus to a different point or at a different distance from the lens. This can be a particular problem if the laser is to be focused miles, hundreds of miles, or thousands of miles away.
Due to these factors, the quest to produce a simple device utilizing these diode lasers producing a useful, single output beam has, to date, eluded the scientific and technology worlds. Other methods have been tried and have had success in this goal. This has limited the usefulness of diode lasers for a number of useful applications, including high-power applications. The prior art diode lasers have not produced a useful, simple to implement, single output beam device, and such a result has eluded the scientific and technology worlds. It would be useful to provide a device that overcomes one or more of these problems.
Various prior art methods of collating the outputs of laser emitters have been used with various levels of success, and all with substantial shortcomings. U.S. Pat. No. 6,782,016, incorporated by reference, discloses injection synchronizing a plurality of pulsed broad area lasers using a signal source; modulating the plurality of pulsed broad area lasers using the signal source; and externally coupling the plurality of pulsed broad area lasers. U.S. Pat. No. 6,813,069, incorporated by reference, discloses a refractive index matched MOPA scaled fiber array laser. U.S. Pat. No. 6,826,224, incorporated by reference, shows a high power semiconductor array that outputs wavelength matched, phase matched light which uses leakage between individual emitters next to each other in a bar. U.S. Pat. No. 7,203,210, incorporated by reference, uses a liquid crystal light valve on each diode emitter. U.S. Pat. No. 7,212,553, incorporated by reference, uses feedback to frequency lock the diode laser to 1 nanometer bandwidth, for a fiber laser array. But none of these solutions are adequate for all current needs.